Five levels of exogenous proline including 0， 0.25， 0.5， 1 and 2 mmol/L were set for Brassica napus under 150 mmol/L salt stress to study the regulatory mechanism of exogenous proline on the growth and development of rapeseed under salt stress. The effects of exogenous proline on the antioxidant systems， osmotic substances， and content of ion under salt stress were investigated. The results showed that salt stress significantly inhibited the growth of rapeseed. Low concentrations （0.25 mmol/L and 0.5 mmol/L） of exogenous proline promoted the growth of rapeseed. Compared to 0.25 mmol/L exogenous proline， the application of 0.5 mmol/L had a better promoting effect on the growth of rapeseed， reduced Na⁺ accumulation in leaves， increased the content of K⁺， improved the activity of antioxidant enzyme， and reduced the content of reactive oxygen species. In addition， 0.5 mmol/L exogenous proline promoted the accumulation of osmotic substances including proline in rapeseed leaves. The application of high concentrations （1 mmol/L and 2 mmol/L） of exogenous proline not only did not alleviate salt stress， but also caused further damage to rapeseed leaves. It is indicated that salt stress can cause damage to the growth of rapeseed. Applying an appropriate amount of exogenous proline can stimulate the antioxidant system， effectively alleviate the inhibition of salt stress on the growth of rapeseed， and improve its salt tolerance.